In the related art, various sound generating devices have been used for indicating completion of measurement performed by a measuring device and have been used in buzzers and the like. For example, in a sound generating device described in Patent Document 1 (Japanese Unexamined Patent Application Publication No. 2001-199305), a piezoelectric diaphragm is held in a case having an opening that is open upward. The opening is sealed by a cover plate. A bottom plate is disposed below the piezoelectric diaphragm. Acoustic spaces are formed above and below the piezoelectric diaphragm. A sound emitting hole is formed in the above-mentioned cover plate or in a side wall of the case.
In contrast, in a sound generating device described in Patent Document 2 (Japanese Unexamined Patent Application Publication No. 2004-328189), a sound emitting hole is formed in a side wall of a case. A sound emitting pipe having a duct-like shape is formed in the case. The sound emitting pipe is integrally formed with the case. In recent years, measuring devices and the like that are provided with sound generating devices have been reduced in size. Consequently, sound generating devices have been mounted in narrower spaces. In the sound generating device described in Patent Document 1, the sound emitting hole is often formed in the cover plate or in a top plate. Thus, there has been a problem in that, when an inner wall of a case of a measuring device or the like is present in the vicinity of the cover plate or the top plate, the sound pressure decreases due to an increase in air resistance or the like.
In contrast, in the case where a sound emitting hole is formed in a side surface, the sound pressure is less likely to decrease even if a space above the top plate is narrow. However, the sound emitting hole is elongated in a direction toward a side wall of the case, and thus, a sufficient sound pressure cannot be obtained.
Although the sound pressure can be increased by providing the sound emitting pipe having a duct-like shape as described in Patent Document 2, the structure of the sound generating device becomes complex, and two case components are required. In addition, in a configuration in which a sound is emitted toward the side of the case, the sound is less likely to be projected toward the front of the case. That is to say, there is a problem in that the directivity is high.
It is an object of the present invention to provide a sound generating device capable of sufficiently increasing the sound pressure and reducing the directivity of a sound to be emitted even if there is an obstacle in front of a top plate.